Hydraulic accumulator

ABSTRACT

The invention relates to a hydraulic accumulator, especially a piston accumulator, comprising an accumulator housing ( 10 ) and at least one gas chamber ( 12 ) and a fluid chamber ( 14 ), these being separated from each other by a separating element ( 16 ). At least one of these chambers ( 12, 14 ) can be filled with a pressure medium or at least partially emptied of the same through at least one valve control unit ( 26 ) which has a switching valve ( 28, 30 ). The respective switching valve ( 28 ) is accommodated in a corresponding valve location ( 29 ), and can be moved in the direction of movement of the separating element ( 16 ) from an opening position into closing position and vice-versa. The aim of the invention is to avoid an expensive line network between the hydraulic accumulator and the valve control unit, so that sealing or leakage problems such as are common in a line network, never occur, To this end, the valve control unit ( 26 ) is accommodated in a valve block ( 24 ) which is independent from the housing ( 10 ), said valve block ( 24 ) has an additional valve location ( 31 ) for an additional switching valve ( 30 ) for performing another switching task, and the valve locations ( 29, 31 ) are configured essentially identically an(l are situated eccentrically in relation to the longitudinal axis ( 33 ) of the hydraulic accumulator for modular use of the switching valves ( 28, 30 ), which are configured as identical parts.

[0001] The invention pertains to a hydraulic accumulator, especially apiston accumulator, with the features of the preamble of Claim 1.

[0002] One of the main purposes of hydraulic accumulators is, amongother things, to accommodate certain volumes of pressurized fluids of ahydraulic system and to feed these volumes back to the system upondemand. Hydraulic accumulators of this type that are in common useinclude piston accumulators, bladder accumulators, and diaphragmaccumulators, but also weight-loaded and spring-loaded accumulators.Hydraulic accumulators of this kind can be used to perform a variety oftasks, such as storing energy, damping shock, oscillation, andpulsation, recovering energy, compensating for volume flow, etc..

[0003] Valve control units that are commonly equipped with on-off or wayvalves to control the flow of fluid to and from the hydraulicaccumulator are used to operate the hydraulic regulators and controlthem. In this connection the hydraulic accumulator is commonly connectedto pipework by fluid lines that provide the fluid-carrying connectionbetween the accumulator and the valve control unit. Drawbacks of theknown solution, as embodied in a wide variety of designs that arereadily available on the market, include sealing problems owing to thelarge number of connections between the hydraulic accumulator pipeworkand the valve control unit and also the added costs for the network oflines connecting to the fluid lines. Especially under crampedconditions, there are also problems with accommodating the large numberof the above-mentioned components in a reasonable fashion and connectingthem together in such a way that they can carry fluid. Since moreoverdifferent manufacturers produce the hydraulic accumulators, thepipework, and/or the valves of the valve control units, mating problemsin particular arise on the spot where the installation work is actuallydone.

[0004] From DE-A-27 07 469 a hydraulic accumulator is known, especiallyin the form of a device for regulating pressure. The known hydraulicaccumulator accomplishes the tasks of, on the one hand, keeping thepressure in the accumulator at a given level and, on the other,protecting the above-mentioned accumulator against any accidentaloverpressure. To accomplish this, the known hydraulic accumulator has avalve slider like a hollow sleeve located inside a valve recess thatextends along the longitudinal axis of the hydraulic accumulator; saidvalve slider receives the high pressure at its middle and at one of itsends is subjected to the operating pressure that is to be regulated. Atits other end, said valve slider rests against a support body on whichan adjustable spring exerts a counteracting force. Since the surfacearea of the contact circle between the sleeve and the support body issmaller than the surface area of the cross-section of the sleeve itself,the displacements of the sleeve against the spring cause the inletopening through which the high pressure enters to close like an on-offvalve. The known valve arrangement is an integral part of the lower halfof the housing of the accumulator, whereby said lower half can bescrewed together with the upper half of the housing, thereby forming thehousing of the hydraulic accumulator. With the known solution, theseparating element consists of an elastic-rubber diaphragm that isequipped with a closing unit in the middle, so that the switchingdirection of the on-off valve coincides with the direction of motion ofthe separating element. If the on-off valve fails in the case of adesign according to the known solution, for maintenance purposes thevalve block that contains the on-off valve has to be removed togetherwith the lower half of the housing or the appropriate replacement has tobe made; this increases the production and maintenance costs in the caseof a design according to the known solution. Although the valve controlunit with the known on-off valve is designed to be large in terms ofgeometry, only one valve function can be performed in terms oftriggering the separating element.

[0005] For a piston pressure accumulator, especially fordrive-slip-controlled braking systems, DE-A-39 41 241 does propose anon-off valve in the form of a load valve, whereby, in order to savespace, its direction of motion is arranged perpendicular to thedirection of motion of a pressure accumulator piston, as well as to thedirection of motion of a shaped part that surrounds it as a partitionunit for the accumulator and this piston is placed above a monitoringswitch as a motion sensor for the shaped part in a valve block of thevalve control unit of the piston pressure accumulator; with this knownarrangement, however, only a single switching task is accomplished and,in view of the fact that the on-off valve is installed in a transverseposition, the valve control unit still requires a relatively largeamount of room. Moreover, the transverse installation position makes itnecessary to divert the fluid stream, which is undesirable from thestandpoint of fluid mechanics.

[0006] From EP-A-0 816 142 and U.S. Pat. No. 5,342,080 hydraulicaccumulators of this kind are known in accordance with theimplementation of the features of the preamble of Claim 1. Thus, theknown solutions ensure modular installation of the on-off valves, whichare designed as identical parts, so that a number of switching functionscan be performed with respect to a hydraulic accumulator despite thecompact dimensions of the valve control unit. Thus, in particular, theone on-off valve can actuate the separating element, and the respectiveother on-off valve can be used for other purposes, for example, tocontrol the gas volume in the gas chamber of the hydraulic accumulator.To the extent that the known solutions are used in overall devices, therespective other on-off valve can also perform other switching tasksrelating to adjacent fluid-bearing units, for example, in the form ofcooling pumps, hydraulic cylinder devices, etc..

[0007] Since the switching direction of the on-off valves runs parallelto the direction of motion of the separating element as well as in thelongitudinal direction of the hydraulic accumulator, it is possible tocontrol the flows of fluid in ways that are favorable from thestandpoint of fluid mechanics without diverting the flows. Since theon-off valves are designed as identical parts, the valve control unitand also the hydraulic accumulator can be designed in a verycost-effective manner. If a certain on-off valve is not required for acertain use of the hydraulic accumulator, this valve can also be simplyleft out of the design and the recess can be closed off with a fillerplug, or this valve can be used in other ways to guide the fluid. If theactual hydraulic accumulator or its valve control unit fails, thesedevices can be readily detached from one another and replaced with newcomponents so that the overall function of the hydraulic system in theapplication of the hydraulic accumulator is not put at risk.

[0008] Since, with the solutions of this type, the on-off valves areconnected to the corresponding hydraulic accumulator as detachableparts, however, sealing problems can arise, on the one hand, and, on theother, mechanical stress, for example, can cause the respective valvecontrol unit to be separated or torn away from the accumulator housing.

[0009] In view of the relevant state of the art, the object of theinvention is thus, while retaining the above-described advantages, tocreate a hydraulic accumulator that requires little overall installationspace and allows the hydraulic accumulator to be securely connected tothe on-off valves, which are designed as identical parts, while ensuringa secure seal. A hydraulic accumulator with the features of Claim 1 inits entirety accomplishes an object of this nature.

[0010] Because according to the characterizing part of Claim 1 the valverecesses are of essentially the same design, because the control blockwith its extension, in close contact with the inside circumference ofthe accumulator housing, extends into said housing, and because theaccumulator housing rests with its one free end against a shoulder ofthe control block, where the extension originates, secure sealing of theconnection between the accumulator housing and the control blockextension. Moreover, the shoulder makes it possible to position theaccumulator housing precisely with respect to the rest of the controlblock and to ensure that the accumulator housing is safely guided alongthe extension of the control block. Accidental detachment of theaccumulator housing from the valve control unit is thus reliablyprevented.

[0011] In another preferred embodiment of the hydraulic accumulatoraccording to the invention, the control block forms the boundary for thefluid chamber by means of its extension, whereby the control block hasat least one fluid channel that empties with its free end into the fluidchamber and is connected with its other free end to the on-off valve.Since the control unit makes a transition directly into the fluidchamber, the free paths for the pressure medium are kept short, thusensuring fast reaction times for the hydraulic accumulator.

[0012] The dependent claims describe other favorable embodiments.

[0013] The hydraulic accumulator according to the invention is explainedin greater detail below based on the drawing.

[0014] The single FIGURE, which is an outline and is not drawn to scale,shows, partly in section and partly in plan, a longitudinal view of thehydraulic accumulator.

[0015] The hydraulic accumulator according to the FIGURE is designed asa piston accumulator. This accumulator has an accumulator housing 10with a gas chamber 12, located therein, and a fluid chamber 14. The gaschamber 12 is separated from the fluid chamber 14 by a separatingelement 16 in the form of a piston part that can be moved longitudinallyalong the inside circumference of the accumulator housing 10 so that thespatial relationship between the gas chamber 12 and the fluid chamber 14is kept variable. In order to be able to store a large quantity ofworking gas in the gas chamber 12, the separating element 16 is designedas a hollow part and on the inside has a corresponding recess 18. In thedirection facing toward the FIGURE, the gas chamber 12 is closed at thetop by a cover part 20, which has a center hole 22, through which theworking gas, for example, nitrogen gas, can be brought into the gaschamber 12. The corresponding center hole 22 is then sealed gas-tight bymeans of a closing valve or similar device (not shown), whereby thequantity of gas in the gas chamber 12 can also subsequently be checkedand supplemented periodically via the closing valve.

[0016] At the opposite end of the accumulator housing 10 is the valvecontrol unit, referred to overall as 26, which is in the form of acontrol block 24. The valve control unit 26 has two on-off valves,whereby the reference number of the first on-off valve is 28, and thenumber 30 refers to the second on-off valve. The corresponding valvecontrol unit 26 is also an integral part of the accumulator housing 10,whereby for this purpose there is a control block 24 with a projection32 which, in direct contact with the inside circumference of theaccumulator housing 10, extends into said housing. Moreover, theaccumulator housing 10 rests with its one free end 34 against a shoulder36 of the control block 24, whereby extension 32 originates at saidshoulder. Compared to the rest of the outside diameter of the controlblock 24, the extension 32 that extends into the accumulator housing isreduced in diameter in accordance with the decrease in size via theshoulder 36.

[0017] The hydraulic accumulator according to the invention is thuscharacterized by the fact that the valve control unit 26 is housed in avalve block 24 that is self-contained relative to the housing 10, thevalve block 24 has another valve recess 31 for another on-off valve 30,which performs another switching task, and the valve recesses 29, 31 aredesigned essentially alike and are arranged off-center from thelongitudinal axis 33 of the hydraulic accumulator to ensure the modularinstallation of the on-off valves 28, 30, which are designed asidentical parts.

[0018] With the upper end of the extension 32, the control block 24limits the fluid chamber 14 in the downward direction in the directionfacing toward the FIGURE. The accumulator housing 10, the chambers 12and 14, the cover part 20, the piston part 16, and the extension 32 aredesigned essentially as cylindrical components and extend along a commonlongitudinal axis 38 of the hydraulic accumulator. The control block 24also has a fluid channel 40, which is arranged off-center from thelongitudinal axis 38 and which empties with its one free end into thefluid chamber 14 and is connected with its other free end to the firston-off valve 28. Running transverse to the fluid channel 40, there is inthe control block 24 a transverse connection 42 to which a fluid line,for example, as part of a hydraulic circuit, could be connected. Thefirst on-off valve 28 is then connected between the transverseconnection 42 and the fluid channel 40, whereby the fluid-carryingconnection between the transverse connection 42 and the fluid channel 40is open in the one switch position and is closed in the other switchposition. Preferably the first on-off valve 28 is accordingly designedas a so-called 2/2-way valve. It would also be conceivable, however, toinstall other valves here, such as way-slider valves, valves withdamping systems, etc., depending on the particular application.

[0019] Installed in the same position relative to the first on-off valve28 is another second on-off valve 30 next to it, which in this case isalso designed as a 2/2-way valve. The second on-off valve 30 has twolateral connections 44, 46 which, like the transverse connection 42,extend sideways radially out from the control block 24. The two lateralconnections 44, 46 are in turn separated from one another by theswitching parts of the second on-off valve 30. When the second on-offvalve 30 is switched through, the lateral connections 44, 46 areconnected together to carry fluid or are separated from one another withthe valve in the blocking position. With the corresponding second on-offvalve 30, it would then be possible, for example in an embodiment notshown here, to actuate of the entry and exit of the working gas in thegas chamber 12 to the extent that the connections 44, 46 are connectedto the gas chamber 12 in such a way as to carry fluid via connectionpoints in the cover part 20. In another embodiment, not shown here, itcould also be possible for the second on-off valve 30 to actuate anotherassembly in the hydraulic circuit, for example, in the form of ahydraulic working cylinder or the like.

[0020] In the embodiment in question here, the on-off valves 28, 30 aredesigned as magnetic valves 48 that can be actuated electrically byconnections 50. Since the above-mentioned magnetic valves 48 are part ofthe state of the art, it is not necessary to go into further detailregarding them.

[0021] The hydraulic accumulator according to the invention provides acomplete solution that allows a compact design. In the embodiment shown,the first and second on-off valves 28, 30 are axially arrangedessentially parallel to the longitudinal axis 38 of the hydraulicaccumulator in the control block 24. Other installation positionstransverse to the longitudinal axis would, however, also be possible,especially in the radial direction. The fact that the accumulatorhousing 10 is in direct contact with the control block 24 means thatleakage is avoided and expensive, labor-intensive pipework is notnecessary. Since the control block 24 with its extension 32 extendsdirectly into the fluid chamber 14 of the accumulator housing 10, inparticular the first on-off valve 28 is located right next to the fluidchamber 14 and is separated only by the fluid channel 40, which is keptshort by design, so that very short activation times can be expected forthe hydraulic accumulator.

1. A hydraulic accumulator, especially a piston accumulator, with anaccumulator housing (10) and at least one gas chamber (12), locatedtherein, and a fluid chamber (14), which are separated from one anotherby a separating element (16), whereby at least one of said chambers (12,14) can be filled with a pressure medium via a valve control unit (26)that has at least one on-off valve (28, 30) and said medium can be atleast partially drained therefrom via said valve control unit andwhereby the corresponding on-off valve (28) is housed in an appropriatevalve recess (29), whereby said on-off valve can move from an openposition to a closed position in the direction of motion of theseparating element (16) and vice versa, characterized by the fact thatthe valve control unit (26) is housed in a valve block (24) that isself-contained relative to the housing (10), the valve block (24) hasanother valve recess (31) for another on-off valve (30), which performsanother switching task, and the valve recesses (29, 31) are designedessentially alike and are arranged off-center from the longitudinal axis(33) of the hydraulic accumulator to ensure modular installation of theon-off valves (28, 30), which are designed as identical parts.
 2. Thehydraulic accumulator as claimed in claim 1, wherein the control block(24) with an extension (32), in direct contact with the insidecircumference of the accumulator housing (10), extends into said housingand the accumulator housing (10) rests with its one free end (34)against a shoulder (36) of the control block (24), where the extension(32) originates.
 3. The hydraulic accumulator as claimed in claim 2,wherein with its extension (32) the control block (24) limits the fluidchamber (14) and the control block (24) has at least one fluid channel(40), which with its one free end empties into the fluid chamber (14)and with its other free end is connected to the on-off valve (28). 4.The hydraulic accumulator as claimed in one of claims 1-3, wherein theother on-off valve (30) is connected to the gas chamber (12) andactuates the entry or exit of the working gas or takes over the functionof fluid control for another assembly.
 5. The hydraulic accumulatorclaimed in one of claims 1-4, wherein the on-off valves (28, 30) aredesigned as 2/2-way valves.
 6. The hydraulic accumulator as claimed inclaim 5, wherein the 2-2-way valves are designed as magnetic valves (48)and can be activated electrically.
 7. The hydraulic accumulator asclaimed in one of claims 1-6, wherein said accumulator is designed as apiston accumulator with a separating piston as a separating element(16).
 8. The hydraulic accumulator as claimed in one of claims 1-7,wherein the accumulator housing (10) and the control block (24) aredesigned essentially as cylindrical components.
 9. The hydraulicaccumulator as claimed in one of claims 1-8, wherein the on-off valves(28, 30) can be switched regardless of the positions of the separatingelement (16), whereby said positions are determined by the pressureconditions.